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991.
A concise total synthesis of (+)-deoxocassine (1) and (−)-deoxoprosophylline (2) has been achieved for the first time from d-xylose. The key steps involved in these synthesis are alkyl Grignard reaction, SN2 substitution of mesylate by azide, Wittig reaction, and reductive amination. 相似文献
992.
《Analytical letters》2012,45(15):2733-2742
Abstract A simple flow-injection spectrophotometric method for the determination of thioridazine is described. The method is based on the oxidation of thioridazine with phosphotungstic acid in hydrochloric acidic media. Concentrations of thioridazine in the range 10 – 60 ppm are determined with a relative standard deviation of 1.1%. The method was applied to the determination of thioridazine in pharmaceutical formulations. 相似文献
993.
Stereo- and enantioselective syntheses of (+)-harveynone and (−)-asperpentyn are reported. 相似文献
994.
Kamila Malecka Iwona Grabowska Jerzy Radecki Anna Stachyra Anna Góra‐Sochacka Agnieszka Sirko Hanna Radecka 《Electroanalysis》2012,24(2):439-446
The working principle of a genosensor is based on the mechanism of ion‐channel mimetic sensors. The analytical signals generated upon hybridization processes were recorded by a redox active marker [Fe(CN)6]3?/4? present in the sample solution using voltammetric techniques. The developed genosensor was suitable for determination of 20‐mer complementary oligonucleotide sequence, and also of the PCR products containing the complementary 20‐mer sequence in various positions, with detection limits in the 10 pM range. The noncomplementary 20‐mer oligonucleotide sequence as well as the PCR product without complementary region generated very weak response. The good discrimination of the position of the complementary part in the PCR products was observed. 相似文献
995.
996.
《Analytical letters》2012,45(8):1433-1455
Abstract A method was developed for separation and analysis of corrosion products formed on the surface of Cu-Ni alloys immersed in sea water polluted by sulphide ions. This method is based on the selective dissolution of oxidation compounds by suitable solvents dissolving the metal matrix only to a negligeable extent. The following solvents were used: 1) methanol to dissolve Na+, Cu2+, Ni2+ chlorides and sulphates; 2) glycine to dissolve bivalent metal compounds - Cu2+, Ni2+ oxides, sulphides, oxysulphates, oxychlorides and oxycarbonates; 3) ammonia solution to dissolve Cu+ compounds (i.e. Cu2O and CuCl); 4) potassium cyanide to dissolve CU+ sulphides. Reasonable agreement between chemical and X-Ray analysis results was observed only for copper compounds, since nickel and iron compounds could not tie observed by X-Ray diffraction. The results of Auger and chemical analyses better agree with each other, yet no Fe compounds could be detected. This is to be attributed to the non-homogeneous corrosion layer which notably contains Fe compounds in the innermost region at a depth where Auger spectroscopy is unable to detect them, whereas their detection is possible by chemical analysis, since it is a bulk analysis. 相似文献
997.
《Analytical letters》2012,45(17):3138-3146
Abstract A new, simple, and sensitive method for the determination of riboflavin based on the single-sweep polarographic reduction wave of the photolysis products of riboflavin has been developed. Under the irradiation of an iodine-tungsten lamp, the photolysis reaction of riboflavin in pH 9.3 NH3-NH4Cl buffer solution can be complete in about 20 min. The reaction products yield a single adsorptive reduction wave at ?0.63 V (vs. SCE) negative to the reduction wave of riboflavin by 0.18 V. The derivative wave height is linearly proportional to the concentration of riboflavin in the range of 0.01–17.5 µg/mL (correlation coefficient 0.996). The detection limit is 0.00 5µg/mL. The proposed method has been applied to the determination of multivitamin tablets with satisfactory results. In comparison with the methods directly using the reduction wave of riboflavin for the determination, this method eliminates the effect of the degradation of riboflavin on the determination accuracy and is much more sensitive. The new method could be useful in many fields. 相似文献
998.
In this note,we present that:(1)Let X=σ{Xα:α∈A} be|A|-paracompact (resp.,hereditarily |A|-paracompact).If every finite subproduct of {Xα:α∈A} has property b1 (resp.,hereditarily property b1),then so is X.(2) Let X be a P-space and Y a metric space.Then,X×Y has property b1 iff X has property b1.(3) Let X be a strongly zero-dimensional and compact space.Then,X×Y has property b1 iff Y has property b1. 相似文献
999.
Suppose we are given finitely generated groups Γ1,…,Γm equipped with irreducible random walks. Thereby we assume that the expansions of the corresponding Green functions at their radii of convergence contain only logarithmic or algebraic terms as singular terms up to sufficiently large order (except for some degenerate cases). We consider transient random walks on the free product Γ1* … *Γm and give a complete classification of the possible asymptotic behaviour of the corresponding n‐step return probabilities. They either inherit a law of the form ?nδn log n from one of the free factors Γi or obey a ?nδn?3/2‐law, where ? < 1 is the corresponding spectral radius and δ is the period of the random walk. In addition, we determine the full range of the asymptotic behaviour in the case of nearest neighbour random walks on free products of the form $\mathbb{Z}^{d_1}\ast \ldots \ast \mathbb{Z}^{d_m}Suppose we are given finitely generated groups Γ1,…,Γm equipped with irreducible random walks. Thereby we assume that the expansions of the corresponding Green functions at their radii of convergence contain only logarithmic or algebraic terms as singular terms up to sufficiently large order (except for some degenerate cases). We consider transient random walks on the free product Γ1* … *Γm and give a complete classification of the possible asymptotic behaviour of the corresponding n‐step return probabilities. They either inherit a law of the form ?nδn log n from one of the free factors Γi or obey a ?nδn?3/2‐law, where ? < 1 is the corresponding spectral radius and δ is the period of the random walk. In addition, we determine the full range of the asymptotic behaviour in the case of nearest neighbour random walks on free products of the form $\mathbb{Z}^{d_1}\ast \ldots \ast \mathbb{Z}^{d_m}$. Moreover, we characterize the possible phase transitions of the non‐exponential types n log n in the case Γ1 * Γ2. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2012 相似文献
1000.
FRIED Michael D. 《中国科学 数学(英文版)》2012,55(1):1-72
Davenport’s Problem asks:What can we expect of two polynomials,over Z,with the same ranges on almost all residue class fields? This stood out among many separated variable problems posed by Davenport,Lewis and Schinzel.By bounding the degrees,but expanding the maps and variables in Davenport’s Problem,Galois stratification enhanced the separated variable theme,solving an Ax and Kochen problem from their Artin Conjecture work.Denef and Loeser applied this to add Chow motive coefficients to previously introduced zeta functions on a diophantine statement.By restricting the variables,but leaving the degrees unbounded,we found the striking distinction between Davenport’s problem over Q,solved by applying the Branch Cycle Lemma,and its generalization over any number field,solved by using the simple group classification.This encouraged Thompson to formulate the genus 0 problem on rational function monodromy groups.Guralnick and Thompson led its solution in stages.We look at two developments since the solution of Davenport’s problem.Stemming from MacCluer’s 1967 thesis,identifying a general class of problems,including Davenport’s,as monodromy precise.R(iemann)E(xistence)T(heorem)’s role as a converse to problems generalizing Davenport’s,and Schinzel’s (on reducibility).We use these to consider:Going beyond the simple group classification to handle imprimitive groups,and what is the role of covers and correspondences in going from algebraic equations to zeta functions with Chow motive coefficients. 相似文献